I was actually debating this sort of thing some months ago. I have cleaned a couple of pipes with isopropyl and still smoke them. They havent killed me yet. I have found that Everclear is best when it is available, however if you go to some places online you can get pipe sweetener which will do essentially the same thing as Everclear of isopropyl and is made specifically for that purpose. I know pipes and cigars sells a bottle of the stuff but I cant remember what it is called. You can actually also use any kind of high proof alcohol as well, such as Bacardi 151 or any other kind of rum, gin, or vodka.